Connected: An Internet Encyclopedia
RFC 1774 - Applicability of BGP

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### Applicability of BGP

In this section we'll try to answer the question of what environment is BGP well suited, and for what is it not suitable? Partially this question is answered in the Section 2 of [1], where the document states the following:

"To characterize the set of policy decisions that can be enforced using BGP, one must focus on the rule that an AS advertises to its neighbor ASs only those routes that it itself uses. This rule reflects the "hop-by-hop" routing paradigm generally used throughout the current Internet. Note that some policies cannot be supported by the "hop-by-hop" routing paradigm and thus require techniques such as source routing to enforce. For example, BGP does not enable one AS to send traffic to a neighbor AS intending that the traffic take a different route from that taken by traffic originating in the neighbor AS. On the other hand, BGP can support any policy conforming to the "hop-by-hop" routing paradigm. Since the current Internet uses only the "hop-by-hop" routing paradigm and since BGP can support any policy that conforms to that paradigm, BGP is highly applicable as an inter-AS routing protocol for the current Internet."

While BGP is well suitable for the current Internet, it is also almost a necessity for the current Internet as well. Operational experience with EGP showed that it is highly inadequate for the current Internet. Topological restrictions imposed by EGP are unjustifiable from the technical point of view, and unenforceable from the practical point of view. Inability of EGP to efficiently handle information exchange between peers is a cause of severe routing instabilities in the operational Internet. Finally, information provided by BGP is well suitable for enforcing a variety of routing policies.

Rather than trying to predict the future, and overload BGP with a variety of functions that may (or may not) be needed, the designers of BGP took a different approach. The protocol contains only the functionality that is essential, while at the same time provides flexible mechanisms within the protocol itself that allow to expand its functionality. Since BGP was designed with flexibility and expandability in mind, we think it should be able to address new or evolving requirements with relative ease. The existence proof of this statement may be found in the way how new features (like repairing a partitioned autonomous system with BGP) are already introduced in the protocol.

To summarize, BGP is well suitable as an inter-autonomous system routing protocol for the current Internet that is based on IP (RFC 791) as the Internet Protocol and "hop-by-hop" routing paradigm. It is hard to speculate whether BGP will be suitable for other environments where internetting is done by other than IP protocols, or where the routing paradigm will be different.

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Connected: An Internet Encyclopedia
RFC 1774 - Applicability of BGP